Several different types of fuel cells are common in the art. In one type, such as phosphoric acid fuel cells and potassium hydroxide fuel cells, the electrolyte is liquid. In a PEM fuel cell, a thin film, electrode consists of a catalyst and a proton exchange membrane, or it may use a more conventional gas diffusion electrode having a catalyst, a proton exchange membrane and a hydrophobic polymer, such as TEFLON.RTM.. Because of its solid electrolyte, the PEM fuel cell has inherent pressure and safety advantages over cells that utilize liquid acid or alkaline electrolytes, for use in some environments, such as in electrically powered vehicles. Solid electrolyte is stable, can withstand greater pressure differentials, and does not leach from the cell. However, water management is required to keep the anode and the proton exchange membrane wet, and to prevent the cathode from flooding, and thereby blocking the oxidant from reaching the cathode. Examples are shown in U.S. Pat. Nos. 4,769,297 and 5,503,944.
When any fuel cell is utilized in an isolated environment, it may be subject to extreme winter temperatures, including temperatures well below 0.degree. C. (+32.degree. F.). In fact, it may be as low as -40.degree. C. (-40.degree. F.) whereas the fuel cell may not operate below about 0.degree. C. (+32.degree. F.). And the water remaining from prior operation may form solid ice, thus preventing reactants from reaching the electrodes. In U.S. Pat. No. 5,798,186, minimal operation of a PEM fuel cell at -10.degree. C. (-24.degree. F.) with an electric heater as a load, warms the fuel cell to above-freezing temperature.
A fuel cell which is to be used to power an electric vehicle must of necessity be as simple, small and light weight as possible. That means that any accessories utilized to pre-heat the fuel cell, which is certainly required in all sub-freezing climates, must also be extremely light and compact.